The present invention relates generally to water treatment systems. More particularly, the present invention relates to electrocoagulation systems for removal of undesirable substances from a treatment stream.
Electrocoagulation has been used in water treatment, particularly wastewater treatment for many years, and the processes involved are well known to those skilled in the art. An electrical potential is applied between a cathode and an anode positioned so as to create an electric field in the water stream, the water and dissolved substances therein being an electrolyte. If at least one of the cathode and anode is sacrificial, ions therefrom migrate into the electrolyte and bond with impurities to create precipitates, which can be physically removed from the water stream by means such as floatation, sedimentation and filtering. Moreover, disassociation of water molecules forms oxygen in multiple forms, hydrogen and hydroxyls, which several species can also be involved in beneficial reactions, e.g. oxidation-reduction reactions, and can also interact with biologics, if present, with treatment effect. Moreover, microbubbles formed can physically interact with suspended materials and forming precipitates to aid in removal by floatation or aggregation. The process has other uses, such as breaking emulsions, and other known applications known to those skilled in the art.
Various alternatives are known. As another example, depending on the water treatment stream to be treated, additives can be used. These can be used with non-sacrificial cathodes and anodes to form ions to interact with solutes and particulate matter in coagulating out of suspension and solution the impurities desired; or with sacrificial cathodes and anodes, to enhance the process in some way. As an example, salts can be added to increase the conductivity of the water stream to enhance electrocoagulation processes, which salts also are typically later removed, or are involved in the chemical processes and form precipitates.
As is known, treatment of various water streams containing numerous kinds of impurities, including heavy metals and other undesirables can be enhanced using the technique. For this reason electrocoagulation processes (sometimes called by other names) have been used in mining, food processing, manufacturing, and other industrial applications in addition to sewage and other water treatment applications.
Further, it is known that applying the electric field to the water stream in and of itself can kill at least some microorganisms suspended therein, for example by means of the osmotic pressure exerted on cell walls. Contact with oxygen species generated, and also with other species and reaction products that may be generated, can have a biocidal effect. Also, as precipitates and accreted bubble/precipitate/suspended materials complexes form, microorganisms may also be caught up in and trapped in coagulating materials and be carried out with the precipitates. So electrocoagulation can have at least some biological treatment effects as well.
For the process to be economically viable, it must be efficient, as large amounts of power may be needed to create the fields and electrochemical effects necessary to the process. Therefore improvements in effectiveness of the process, and decreases in downtime for maintenance and electrode (cathode or anode, or both) replacement are highly desirable.
Further, to the ends of efficiency, the process is usually used with fairly consistent treatment streams, so that it can be tailored to a particular stream having a particular overall chemical makeup and set of contaminants to be removed. The process is tuned to the waste stream by optimizing the voltage, electrode materials, additives (if any), flow regime (fast, slow, turbulent, laminar, etc.) to get the best results. While this works well for particular unchanging water streams to be treated, it does not lend itself to variable treatment streams which can change in temperature, pH, chemical and biological makeup, and in undesirable impurities to be removed.